Erythromycin, C37H67NO13, molecular weight of 733.94, is an antibiotic having a 14-membered macrolide ring. It has an antimicrobial spectrum similar to or slightly wider than that of penicillin and has a strong antibacterial effect against the G+ bacteria. It can be used as a raw material for preparing erythromycin-containing material or a starting material for preparing erythromycin derivatives.

CN1513864A discloses a dynamic recrystallization method for preparing erythromycin from an erythromycin salt, which uses acetone and water as solvents. The amount of erythromycin A in the product formed is less than 93%. The amount of water in erythromycin crystals is more than 3.5%. The microbiological titre of the erythromycin crystals is less than 930 μ/mg.
This invention uses a new solvent to obtain erythromycin having a better quality. The amount of erythromycin A in the erythromycin crystals (HPLC detection method) is more than 94.5%. The amount of dichloromethane in the erythromycin crystals is less than 600 ppm. The amount of water in the erythromycin crystals is less than 2.5%. The microbiological titre of the erythromycin crystals is more than 940 μ/mg.